SECRETION OF SHIGELLA-FLEXNERI IPA INVASINS ON CONTACT WITH EPITHELIAL-CELLS AND SUBSEQUENT ENTRY OF THE BACTERIUM INTO CELLS ARE GROWTH STAGE-DEPENDENT
J. Mounier et al., SECRETION OF SHIGELLA-FLEXNERI IPA INVASINS ON CONTACT WITH EPITHELIAL-CELLS AND SUBSEQUENT ENTRY OF THE BACTERIUM INTO CELLS ARE GROWTH STAGE-DEPENDENT, Infection and immunity, 65(2), 1997, pp. 774-782
Upon contact with the surface of epithelial cells, Shigella flexneri s
ecretes Ipa proteins through the Mxi-Spa type In secretion apparatus.
Among the Ipa proteins, IpaB and IpaC form a soluble complex in the ba
cterial supernatant which appears to be sufficient to initiate the cel
lular rearrangements necessary to achieve bacterial entry. Here, we pr
ovide the first evidence that efficiency of bacterial entry into cells
depends on the stage of bacterial growth. Bacteria in the early phase
of exponential growth are six times more invasive than those in the s
tationary phase. The entry efficiency of the bacteria present on the c
ell surface appears to correlate with the percentage of those that are
able to secrete their invasins. This suggests that the capacity to ac
tivate the Mxi-Spa apparatus is a major factor in the regulation of ba
cterial entry efficiency. Consistent with these observations, we have
further shown that bacteria which have reached the stage of division s
ecrete Ipa proteins more often than those that have not. Also, initial
secretion occurs essentially in the area of the septation furrow. The
Ipa proteins, secreted in the vicinity of the septation furrow, seem
to initiate the early stages of reorganization of the host cell cytosk
eleton.